Here’s how the government pushes companies to treat kids and rare diseases

BioMarin Pharmaceutical in Novato and San Rafael has six more months to keep exclusively selling a new, kid-friendly form of its drug for a disease called phenylketonuria.

Haven’t heard of phenylketonuria? That’s because it’s a rare genetic disorder that only affects 10,000 to 15,000 people in the United States, which makes it a so-called “orphan” disease (in the U.S, these are disorders that affect fewer than 200,000 people).

Patients with phenylketonuria can’t process an amino acid called phenylalanine found in many foods, so it ends up building up in the blood. Left untreated, high blood phenylalnine levels can affect the brain, impair thinking and cause behavioral problems.

Why did the FDA grant BioMarin this permission, known in bureaucratic lingo as a “six-month pediatric exclusivity extension”?

The reason BioMarin is in the business of rare diseases in the first place goes back to 1983, when the nation passed the Orphan Drug Act. Before then, few companies made drugs for orphan diseases because there were relatively few patients who would buy the treatments. To motivate companies to make drugs for these diseases, the law gave such companies the right to sell the therapy for seven years without competition.

Another problem: Pharmaceutical companies have historically been reluctant to do clinical trials on children. The market for children patients is small (compared to adults), and it’s hard to get informed consent (kids may not understand what’s going on during a trial).

Another law has therefore tried to create incentives for companies in a way similar to the Orphan Drug Act: by giving them an extra six months to sell a drug if they submit clinical studies that involve children. This is on top of any patent rights under the Orphan Drug Act.

In this case, BioMarin did trials on patients from birth to age 6 at the FDA’s request. Why so young? The American College of Medical Genetics and Genomics recently issued new guidelines that say that patients with phenylketonuria should start on treatment as early in life as possible and stay on it for life.